The pair, believed to be a mother and her three-month-old child, were found by a family member this morning.
Police were called to the home on Robinson Road in Morley about 11.10am, and part of the street was closed to the public.
“Upon arrival an adult female and an infant child were located deceased,” Western Australia Police said in a statement.
“Major Crime Division detectives are investigating the circumstances surrounding the two deaths.”
One neighbour said they heard a lot of sirens, while another told 9News they counted six police cars and three ambulances.
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Authorities cordoned off the property and removed items in evidence bags.
Neighbours said the residents mostly kept to themselves.
“I’ve been here for 37 years and it’s always been quiet and we’ve had no drama,” one local said.
Readers seeking support can contact Lifeline on 13 11 14 or beyond blue on 1300 22 4636. Suicide Call Back Service 1300 659 467. MensLine Australia 1300 78 99 78.